The present invention generally relates to a flow amount measuring and controlling apparatus to be included in a gas meter. The amount of gas flow is observed so as to estimate what type of gas appliance is being used from the changes in the amount of gas flow so that the gas may be shut off when the gas appliance has been judged to be used in an abnormal way.
In order to prevent a gas explosion accident, gas meters have recently been utilized which have microcomputers built in, and have a function of shutting off the gas when gas appliances are judged to be abnormally used and raw gas is judged to be released, from the changes in amount of gas flow. Such a conventional gas meter with a safety function attached to it detects changes in the amount of gas flow passing through the gas meter, so as to recognize whether a gas appliance of a capacity equivalent to the size of the change has been ignited or put out. The gas supply is adapted to be shut off when the above described gas appliance has been continuously used beyond a maximum time which is previously set in accordance with the capacity of the recognized gas appliance.
But such a conventional gas meter with a safety function attached to it has a problem shown hereinafter. A modern gas appliance has not only two changes of ignition/extinction, but also continuous changes in the amount of flow during use in accordance with the situation, for example, when a gas fan heater is used to raise the ambient temperature, the combustion amount of the gas fan heater gradually becomes lower as the ambient temperature rises. When the amount of gas flow of a first gas appliance has been reduced during use, the conventional gas meter with a safety function attached to it recognizes the changes in the amount of flow as the extinction of the above described first gas appliance and the ignition of a second gas appliance of a smaller capacity. When the amount of gas flow of the above described first gas fitting has been increased during its use, a third gas fitting equivalent in capacity to the increase in the amount of flow is recognized to have been ignited. As a result, in spite of the fact that a first gas appliance is actually burning with a large amount of gas flow, the gas meter recognizes two gas appliances, the second and third gas appliances of a smaller capacity, as being used. The maximum time for the continuous use of the first gas fitting is elongated, with problems in that the dangers forgetting to turn off gas appliances and raw gas releasing, cannot be prevented. A gas hot water heater with a larger combustion capacity to be set outdoors is used for various applications such as a bath, a shower, dishwashing in a kitchen, and so on. It is often used continuously more than one hour. In such an appliance to be set outdoors, the maximum time of continuous use may be desired to be set especially longer, differently from indoor appliances. This kind of use can be settled without problem if the type of the gas appliance in use at the present time can be recognized correctly.
The power demand is recently increased at summer time by the spread of air conditioner using electric power; this results in insufficient power supply capacity. On the other hand, the gas demand is likely to be reduced at summer time. Therefore, there is a tendency of easing the power demand by the spread of air conditioners using gas, and at the same time, of averaging the demand of the gas annually. Thus, a rate policy which makes the gas rate lower in accordance with the amount of gas used for air conditioners has been considered. In order to effect such a rate policy for each appliance, an auxiliary gas meter for measuring the amount of gas flow of the gas air-conditioner is necessary in addition to the main gas meter. The expenditure for the auxiliary gas meter, the expenditures and so on for mounting the auxiliary gas meter onto the gas piping are required. If the type of gas appliances now in use with the main gas meter can be correctly recognized and the amount of gas used can be correctly integrated, a rate policy for each appliance can be realized only by the main gas meter.